There are a number of surgical techniques for treating clouding within the eye lens, which is referred to as a cataract in medicine. The most common technique is phacoemulsification, in which a thin needle is introduced into the diseased lens and excited to vibrate by means of ultrasound. The vibrating needle emulsifies the lens in its direct vicinity in such a manner that the created lens particles can be suctioned away through a line by means of a pump. In the process, a rinsing fluid (irrigation fluid) is supplied, with the particles and the fluid being suctioned away through an aspiration line, which is usually arranged within the needle. Once the lens has been completely emulsified and removed, a new artificial lens can be inserted into the empty capsular bag, and so a patient treated in this manner can regain good visual acuity.
Surgery on the clouding within the lens or cataract surgery is an intervention with a relatively low rate of complications and high patient numbers. In Germany, approximately 600 000 operations are carried out each year, with the clouded lens being replaced by an artificial lens implant. However, the relatively low rate of complication can only be achieved if an operator with lots of experience carries out the operation. During the operation, it proves impossible to prevent a relatively large particle from positioning itself in front of the needle tip in such a way, while the lens is being broken up by means of a needle tip vibrating with ultrasound, that the needle tip or the suction opening thereof becomes blocked. This state is referred to as occlusion. In such a case, the suction pressure within the aspiration line increases substantially, with emulsification being interrupted at this time. Only once the particle has been removed again from the needle tip, for example as a result of a very high energy input, a significant increase in the suction pressure or a reversal of the aspiration pump running direction, can conventional suctioning away of the fluid and the small particles take place. At such a time, a blockage is therefore lifted, with the previously applied high negative pressure reducing instantaneously. The suction created thereby can lead not only to small particles and fluid being pulled toward the aspiration needle but also to part of the capsular bag coming into contact with the needle. The piercing of the capsular bag leads to significant complications for the patient; this needs to be avoided at all costs. An experienced surgeon has, over time, developed a sense for when an occlusion is just about to foe broken up. Nevertheless, there always is a risk of the patient's eye being injured.